Journal of the Department of Agriculture, Journal of the Department of Agriculture, Western Australia, Series 4 Western Australia, Series 4
Volume 13
Number 3 1972 Article 6
1-1-1972
Effect on bees of insecticides used on rape Effect on bees of insecticides used on rape
A C. Kessell
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Recommended Citation Recommended Citation
Kessell, A C. (1972) "Effect on bees of insecticides used on rape," Journal of the Department of Agriculture, Western Australia, Series 4: Vol. 13: No. 3, Article 6.
Available at: https://library.dpird.wa.gov.au/journal_agriculture4/vol13/iss3/6
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bees of insecticides used on rape
By A. C. Kessell, Senior Instructor, Apiculture Branch
Rapeseed could provide beekeepers in Western Australia with a valuable new honey crop—hut insecticidal spraying of rape at flowering time is a potentially serious threat to most commercial beekeepers.
There are indications that insect pollination may improve rapeseed yields, so both growers and bee- keepers could gain from a co-opera- tive approach to the problem.
Spraying after sundown and pre- venting spray drift to nearby apiaries should avoid most losses.
It is estimated that 70,000 acres of rapeseed were planted in West- ern Australia in 1971. This figure could be extended over the next five years to 280,000 acres.
Insecticidal spraying of rapeseed has already caused some heavy losses and the problem could grow as the area of rapeseed expands.
According to reports from the Eastern States, honey bees find the crop very attractive and will fly up to 5 km (3 miles) over capeweed and Paterson's curse to work rape.
This was confirmed in the Lan- celin area last spring, when a bee- keeper who suffered severe casual- ties through spray estimated that his bees were flying 4 to 5 km (21 to 3 miles) to the crop. Odd cases have been recorded in Cowra,
N.S.W., of bees flying up to 10 km (6 miles) to work rape.
If the crop is so attractive to bees, and the area is to be increased, rape will certainly provide a useful source of nectar for beekeepers in W.A.
Beekeepers who work York gum, cape weed, Paterson's curse or coastal plain crops near developed areas are all likely to have bees within flying range of rape crops.
It is estimated that 60 to 75 per cent of the commercial apiaries in the State would come within the above areas when rape crops are in flower.
The beekeeper who places his hives on the crop with the authori- sation of the land owner may have little to fear from insecticides. His bees are not likely to fly over rape to work an adjoining property. He can ask the owner to advise him of any spraying programmes and move the bees out of the danger area.
However, infestations of native budworm and aphids can build up very rapidly and crops must be sprayed within the shortest possible time to avoid serious damage.
This could mean that a beekeeper may have from 24 to 36 hours to shift his hives. Should he be out of contact when spraying is neces- sary, his bees could suffer.
Honey bee collecting pollen from a rape flower.
The real danger arises where a farmer who does not know of the existence of apiaries in his neigh- bours' paddocks, or on Crown land several miles away, sprays his crop and quite innocently causes untold damage to another primary pro- ducer—the beekeeper.
The field bees caught by the spray may die in the field or, as in the case of demeton-S-methyl
(Metasystox), many may have time to return to the hive before dying.
With some sprays, the nectar may be poisoned for many days after application. Two such types are carbaryl (7 to 11 days) and phos- phamidon (11 days).
On returning to the hive, field bees regurgitate their load of poison nectar. Young, newly emerged bees gorge themselves on this nec- tar and are also killed by the poison. Apart from the death of these bees, and subsequent loss in hive production, there is the loss of bees as cross-pollinators on the crop.
A Metasystox spraying pro- gramme was carried out on a Lan- celin property in the late spring of
1971, and the spray was applied after dark. There were several apiaries within a one-mile radius.
Bees from these apiaries were work- ing the treated crop early the fol- lowing morning and there were no signs of bee losses from these apia- ries.
A trial was conducted at Avon- dale Research Station last year, using insecticides with little known effect on bees. Caged bees were placed in the field and a hand- operated boom sprayer was used to apply each treatment. A high percentage of the bees died quickly, as can be seen from the graph. The toxicity of Metasystox was already known but was used as a guide in assessing the classes of the other three. After 16 hours, only 53 per cent of the bees in the Metasystox group were dead. This would ac- count for bees being able to return to the hive before they died.
Further trials are in progress.
It would appear that most insec- ticides recommended for rape would be less harmful to bees if applied after periods of concentrated ac- tivity by the bees on the crop. As some sprays have residual effect
N o . of bees in c a g e s
6 0
4 0 -
2 0
M e t a s y s f o x
4 5 6 t i m e a f t e r e x p o s u r e - hours
R e c o m m e n d e d insecticides and r a t e per acre for rape seed crops in flower, and t h e i r t o x i c i t y t o bees
Active ingredient Trade name
demeton-S- carbaryl trichlorphon . . .
D D T methyl (Sevin, (Dipterex, T „ ? ' , * Z ? " Toxicity of insecticide t o bees (Metasystox) Dicarbam) Klorfon) (Uitracide)
Name of insect (common
and official) Toxicity Residual Use
effect class
Aphids—Various spp. 8 f I oz Moderate N i l
Cabbage Moth Flutdla 16 fl oz of xylostella (L.) 2 5 % Cone. J
| Alternatives
12 oz of 80", wettable
p o w d e r j
Moderate I day I I
Moderate 7-12 days -f- I high
12 oz of 8 0 % soluble p o w d e r j
Low N i l
* ( b )
(a)
• ( b ) Cabbage Moths and Aphids 16 fl oz of - 8 fl oz
25",, cone.
Moderate I day + I I
Cabbage W h i t e Butterfly Pieris rapae (L.)
Cabbage Centre G r u b Hellula sp.
Native Budworm Heiothis punct/geroWall.
32 fl 2 5 %
oz of C o n c . t
As for Cabbage moth
As for Cabbage moth
l 6 f l o z of 4 0 % concentrate
Moderate to high
N i l M
Moderate t o high
1 day I I
t Alternatives
16 oz of 8 0 % soluble p o w d e r t
Low t o moderate
N i l
20 oz of 8 0 % wettable
p o w d e r t
Moderate 7-12 days'1,, I t o high
Classes: I - Hazardous t o bees at any time.
11—Not hazardous if applied when bees are not foraging.
(a) Because of high rating per acre this classification may have t o be regrouped under Class I and may have a higher residual effect.
(b) Results from trials on Avondale Research Station.
* May be removed f r o m this class after full scale field tests.
85
A typical apiary on agricultural land. Bees from these hives are likely to be within flying range of flowering rape.
lasting one to three hours, spraying would be best carried out after sun- down rather than early morning.
Growers should also avoid spray drift onto an apiary. Beekeepers would be well advised to consider this possibility when siting apiaries, giving consideration to the direction of the prevailing winds in the area at the time of the year.
Attempts have been made to pro- duce an insecticide that will kill the pests and not harm the honey bee.
Trials carried out at Cowra, N.S.W., using endosulfan on rape crops ap- peared at first to give the desired response. Its effects are question- able, however. It has been sug- gested that it could upset the en- vironment by killing the fish in nearby streams.
In New Zealand, legislation has been introduced whereby a farmer wishing to spray insecticide which is harmful to the bees must apply for a permit.
Under section 35 of The New Zealand Apiaries Act, 1969, a farmer is prohibited from applying these sprays to cruciferous or leguminous crops when they are in flower or to flowering plants within the crop, until a permit has been issued by the Department of Agri- culture. Permits are not issued until the applications are investigated so that the necessity to spray is con- sidered and beekeepers have been advised to move their hives from the danger area. Let us hope this will not be necessary in Western Aus- tralia.
However, close liaison between insecticide manufacturers and the Department of Agriculture, together with co-operation of sprayers and beekeepers, will be necessary to avoid disastrous losses of bees work- ing rape crops.
Rapeseed growers may make greater efforts to avoid killing bees working their crops when it is
pointed out that pollination by bees may increase the yield of rapeseed.
Research in rapeseed growing countries in the northern hemis- phere has indicated that under some conditions, particularly in Europe, bee pollination can lead to valuable increases in yield of rapeseed. No such research has been carried out locally, but it is likely that the bene- ficial effects would be much less under our conditions. However, it is logical for rapeseed growers to want to avoid killing pollinating in- sects when there is some likelihood that insect pollination may increase the yield of their crops.
The table gives recommenda- tions for spraying rape. Where possible, information on the toxicity and residual effect on bees has been recorded. The toxicity of some classes is based on the results of last season's trial at the Department of Agriculture's Avondale Research Station, Beverley.
An apiary on open heath north of Lancelin. Rape crops in
developed areas 5 to 6 km (3 to 4 miles) away are being worked by these bees.
